The calculated distance (air line) between T’ongch’ŏn-ŭp and Hyesan is approximately 170 miles respectively 273 kilometers.
By car or train, the actual journey to Hyesan is certainly longer, as only the direct route (as the crow flies) between T’ongch’ŏn-ŭp and Hyesan has been calculated here.
Air line (approximately)
273 kilometers
147 nautical miles